1. Field of the Invention
The present invention relates, in general, to communication systems and methods to support communications and messaging between neighboring base stations that operate networks (e.g., wireless regional area networks (WRANs), cells, or the like), and, more particularly, to a method, and systems/devices configured to perform such a method, for scheduling communications between base stations or control systems of neighboring WRAN or wireless cells or networks. The described method and systems may be used for scheduling connection-based, over-the-air communications between base stations operating in compliance with standards and protocols for wireless networks such as those distributed by the IEEE 802.22 Working Group.
2. Relevant Background
Many countries are striving to provide wireless broadband access or digital cellular communications to all or large portions of their citizens. Much of the population is in rural and remote areas away from cities and urban areas which can receive wireless services with existing infrastructure. Recent studies have indicated in the radio spectrum that licensed bands, such as TV or UHF bands, are underutilized. In the United States, the Federal Communications Commission (FCC) issued the “TV band Notice of Proposed Rule Making (NPRM)” that proposed allowance of unlicensed radios to operate in the TV broadcast bands as long as no harmful interference is caused to incumbent services such as TV receivers. In response, the Institute of Electrical and Electronics (IEEE) formed the IEEE 802.22 working group in 2004 to develop protocols for an interoperable air interface for use in spectrum allocated to TV broadcast service and enable providing wireless services such as broadband access with a point to multipoint wireless regional area network (WRAN). The WRAN system is intended to provide packet-based transport capabilities such as wireless broadband services, i.e., Internet access, data transport, streaming video, VoIP, and other services that are presently available to much of the population using digital subscriber (DSL) technologies or digital cable modems.
WRAN technology has been initially targeted at wireless broadband or remote access for geographically dispersed, sparsely populated areas. The use of TV broadcast bands or UHF bands as a license exempt spectrum for WRAN provides a non-line of sight transmission range of up to 100 kilometers but more typically 30 to 70 kilometers, which is significantly greater than ranges available with WiFi and wireless networks. The target markets or users of the WRAN-based services are single family residential units, multi-dwelling units, small office/home office (SOHO) locations, small businesses, and remote public and private campuses. A WRAN system based on IEEE 802.22 protocols will likely make use, in a non-interfering manner, of unused TV broadcast channels, i.e., TV channels with bandwidths of 6, 7, and 8 MHz in a frequency range of 41 to 910 MHz (e.g., 54 to 862 MHz in the United States with a 6 MHz channel bandwidth).
An IEEE 802.22 system is generally a fixed point-to-multipoint wireless air interface in which the point is a base station (BS) that manages its own cell or coverage area and all associated consumer premise equipments (CPEs) or multipoints. Each CPE represents the user of the wireless services provided by the BS operator. During operations, the BS controls the medium access in its cell such as by setting the channel used for BS and CPE broadcasts to form the wireless link. The BS transmits in the downstream to the various CPEs, which respond back to the BS in the upstream direction, and these communications may be thought of as downlink and uplink communications or signals. The BS and CPE need to be designed to communicate without interfering with licensed or primary users. With this in mind, the BS manages spectrum or channel usage and uses sensing of existing channels to protect incumbent or primary users. To achieve distributed sensing, cognitive radio and/or software defined radio technology provides real-time sensing of spectrum usage. For example, the BS of the WRAN generally will be capable of performing distributed sensing which involves the CPEs sensing the spectrum and sending periodic reports to the BS. The sensing may be in-band to sense on the channel being used by the BS and CPE and/or out-of-band to sensing on the other channels (such as with an omni-directional antenna). Incumbent sensing also generally includes the BS periodically quieting the channel to allow in-band measurements to be carried out. If an incumbent or other use is detected by the BS based on reported measurements and preset interference detection thresholds, the BS makes the decision of whether to continue using the channel or to vacate the channel (i.e., to switch or hop to another vacant frequency). In addition to protecting incumbent or licensed services, WRANs under IEEE 802.22 are unlicensed and a BS servers a large area. As a result, coexistence amongst overlapping or coallocated cells must be managed and controlled by the BSs of the WRAN so that self-interference among neighboring BSs does not render the system useless.
Under IEEE 802.22 and other existing protocol, the issue of communication between neighboring base stations has not been fully addressed or resolved. For example, managing coexistence of WRAN with overlapping coverage areas demands at least periodic communications between the base stations operating the WRAN to effectively control interference, to share sensing information, and to plan channel usage. In some systems of wireless cells or networks, the operators may want to share resources, and this also requires reliable inter-system communications be provided in the systems. It may be feasible in some applications to provide wired communications, such as communications over land-based systems such as the Internet. However, in many systems, the inter-system communications must be mainly or at least partially performed over the air or in a wireless manner. A further difficulty is that neighboring base stations cannot communicate directly due to range or coverage issues.
Hence, there remains a need for improved methods, and devices that implement such methods, for managing communications between neighboring base stations (e.g., between overlapping WRANs). Preferably, such methods and devices would be configured to be compliant with IEEE 802.22 protocols and would be useful in situations where neighboring WRAN share the use of one or more available channels.